为什么这个在IE 上没有弹出来？
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>事件处理程序</title>
</head>
<body>
<div>
<input type="button" value="按钮3" id="btn3" /><!-- /*IE处理程序*/ -->
</div>
<script type="text/javascript">
function showMS(){
alert("Hello java！");
}
var btn3=document.getElementById("btn3");
btn3.attachEvent('onclick',showMS);
</script>
</body>
</html>
